Hello again Rob,
I have had another thought which might help trace your missing Jane and William .
You may or may not be aware that in Scotland during this period married women sometimes retained their birth surnames and did not use their husbands. Apparently there was no legal requirement to change names. Many did ...but you can come across in the Census records a whole family -dad and lots of kids with one surname i.e. Smith and the mum with another i.e. Jones. This doesn't always mean the parents were not married.
Also it was very common on the death of a husband for a woman to revert (if she'd ever changed) to her maiden name. Therefore if William was dead by 1841 Census which I have a funny feeling he could be Jane could be recorded as Jane Hamilton.
There is one Jane Hanilton aged 40 on the 1841 Census at Newton,Midlothian ---not that far from Dalkeith
. She is living at Newton Manse and is a servant working for the Minister John Adamson. This Jane is born outside the county of Midlothian. She is not recorded at the Manse 10 years later. But the Rev. John Adamson is ....and his place of birth is Peebles! Quite a coincidence!
So could this be a widowed Jane Ferguson working (if my calculations are correct
) about 2 to 3 miles away from Dalkeith. Unfortunately due to the lack of info on the 1841 you may never be 100% sure if you've found the right woman, unless she is living with people/relatives you can connect her to.
And of course William could still be alive and the couple could be hiding
and working somewhere else. Looking at the English Census 1841 is another option. Finding a grave/headstone for William might be problematic. I don't know how extensively Scottish graveyards have been researched and transcribed or how available they are online. You don't know where William died?? And they like many many other Scots might not have been able to afford a stone.
Do you have the OPR of Jane and William's marriage? What record do you have of his existence?
Is Jane working as a servant /housekeeper in 1851 and 1861?
Looby